Instability of the Haldane Phase: Roles of Charge Fluctuations and Hund's Coupling

Abstract

We systematically investigate the stability of the symmetry-protected topological (SPT) Haldane phase in spin-1/2 Heisenberg and half-filled Hubbard ladders coupled by ferromagnetic Hund's interactions. Using density-matrix renormalization group (DMRG) method, we analyze key signatures of the Haldane phase: long-range string order, finite spin gap, and characteristic entanglement spectrum degeneracies. In spin-only Heisenberg ladders, we find immediate onset and continuous strengthening of the Haldane phase with increasing Hund's coupling. In contrast, the inclusion of charge fluctuations in Hubbard ladders leads to a nontrivial stability regime, revealing a robust yet bounded region where SPT order persists despite significant charge fluctuations. We identify distinct boundaries separating a trivial insulating phase from the Haldane SPT phase, governed by both Coulomb repulsion and Hund's coupling. Our results highlight the subtle interplay of spin and charge degrees of freedom in correlated itinerant systems and establish essential criteria for observing Haldane physics experimentally in fermionic ladder materials.

arXiv comment6 pages, 5 figures + Supplemental Material

References in corpus (25)

• Entanglement Spectrum as a Generalization of Entanglement Entropy: Identification of Topological Order in Non-Abelian Fractional Quantum Hall Effect States
• Entanglement spectrum of a topological phase in one dimension
• The ITensor Software Library for Tensor Network Calculations
• Classification of Gapped Symmetric Phases in 1D Spin Systems
• Symmetry protection of topological order in one-dimensional quantum spin systems
• Classifying quantum phases using Matrix Product States and PEPS
• Realising the Symmetry-Protected Haldane Phase in Fermi-Hubbard Ladders
• Continuum in the spin excitation spectrum of a Haldane chain, observed by neutron scattering in CsNiCl3
• String order and adiabatic continuity of Haldane chains and band insulators
• Particle-Hole Symmetries in Condensed Matter
• Structure of end states for a Haldane Spin Chain
• Comparative density-matrix renormalization group study of symmetry-protected topological phases in spin-1 chain and Bose-Hubbard models
• The properties of Haldane excitations and multi-particle states in the antiferromagnetic spin-1 chain compound CsNiCl
• Connectivity transition in the frustrated S=1 chain revisited
• Fragility of Symmetry Protected Topological Order on a Hubbard Ladder
• Quadrupolar magnetic excitations in an isotropic spin-1 antiferromagnet
• Doping of a spin-1 chain: integrable model
• Pair-density-wave superconductor from doping Haldane chain and rung-singlet ladder
• Evidence of quantum criticality in the doped Haldane system Y2BaNiO5
• Emergence of Superconductivity in Doped Multiorbital Hubbard Chains
• Spin-1 chain doped with mobile S=1/2 fermions
• Determination of Boundary Scattering, Intermagnon Scattering, and the Haldane Gap in Heisenberg Chains
• Transition to the Haldane phase driven by electron-electron correlations
• Orbital-controlled magnetic transition between gapful and gapless phases in the Haldane system with t2g-orbital degeneracy
• Luther-Emery liquid and dominant singlet superconductivity in the hole-doped Haldane spin-1 chain